Axial piston fluid transmission



AUZ- 24 1954 Y H. EBERT AXIAL PISTON FLUID TRANSMISSION 6 Sheets-Sheet 1 Filed Dec. l1, 1951 vnl...

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Aug. 24, 1954 H, EBERT 2,687,049

AXIA.. PISTON FLUID TRANSMISSION Hei/7 ric/I 56er! .By @gub Allg- 24, 1954 H. EBERT AXIAL PISTON FLUID TRANSMISSION 6 sheets-sheet 3 Filed Dec. 1l, 1951 @l s Z By @am Aug. 24, 1954 H. EBERT 2,587,049

AXIAL PISTONFLUID TRANSMISSION Filed Dec. 11, 1951 6 Sheets-Sheet 4 Pd fen! Aye/1f Aug. 24, 1954 H. EBERT 2,687,049

AXIAL PIsToN FLUID TRANSMISSION Filed Dec. u. 1951 6 Sheets-Sheet 5 y @2ML Aug. 24, 1954 H. EBERT Axm. PIsToN FLUID TRANSMISSION 6 Sheets-Sheet 6 Filed Dec. 11,` 1951 Patented Aug. 24, 1954 UNITED @STATES f PATENT OFFICE AXIAL PISTONFLUID TRANSMISSION Heinrich Ebert, Furth, Germany Application December 11, 1951, Serial No. 261,101

Claims priority, application Germany l December 14, 1950 for the axial pistons. Such an arrangement,`

however, is not suitable for larger transmissions and outputs in as much as the swivel bearings for the swash plates cannot any longer be accommodated properly in view of their necessarily increased size. Furthermore, with transmissions, in which the primary cylinder body as well as the secondary cylinder body are to be driven by means of gears at` different speeds, `the tooth velocities become too great, particularly when transmissions are involved which have a, great speed reduction ratio. e

It is, therefore, an object of this invention to provide an axial piston `fluid transmission which will overcome the above mentioned drawbacks.

`It is another object of this invention to provide an `axial piston iiuid transmission, the output shaft of which is so constructed that the xed or turnable` swash plates, the cylinder bodies pertaining thereto, andthe respective "driving or arresting shafts can easily be accommodated in their respective desired size.` e

e It is a further object of this invention to provide an` axial piston fluid transmission of the above type which will bring about `a` more favorable load distribution for the swivel bearings and allow accommodation of these bearings in the desired `size without affecting the size of the swash `plates or the desireddimensions thereof.

It is `stillanother object to 'provide an axial piston fluid transmission having its primary cylinder body rotated at a speed different from the speed of rotation `of the secondary cylinder reached which latter is produced at higher pres e sures.

e These and other objects and advantages `of the invention will appear more clearly from the following `specification in connection with the acompanying drawings in which:

`2 y Fig. 1 represents a longitudinal section through an axial piston fluid transmission in which .fboth the primary and the secondary cylinder body` is rotated.

Fig. 2 is a longitudinal section through a modi` ned axial piston fluid transmission according to the present invention.

Fig. 3 illustrates a partial section through a l portion of a still further modification of a transmission according to the present invention.

Fig. 4 is a section taken along the line IV-IV of Fig. l.

Fig. 5 represents a section taken along the line V-V of Fig. 1. s l

Fig. 6 is a section taken along the line VIVI of Fig. 1. i

Fig. '7 illustrates a longitudinal section through a further modied transmission according to the In order to overcome the above mentioned drawbacks encountered with the heretofore known axial piston iiuidtransmissions with regard to the accommodation of properly dimensioned swivel bearings for the swash plates and tooth velocities of the driving gears, according to the present invention the output shaft is constructed as a hollow shaft in the interior of which are mounted the fixed or turnable `swash plates as well as the cylinder bodies pertaining thereto and their driving or arresting shafts. In this way, the swivel bearings for the swash plates receive a more favorable load, and these swivel bearings can easily in the desired size and with the necessary dimensions be accommodated within the hollow output shaft without affecting the size of the swash plates.

With transmissions in which the primary as 46 well as the secondary cylinder body is driven at correspondingly different speeds, the gears on the drive shafts can be kept correspondingly small so that also the tooth velocities of the drivpressure spring may be used according to the present invention for pre-loading both cylinder bodies to thereby assure the sealing of the cylinder bodies with regard to the rotatable control valve before the self-sealing becomes effective at higher pressures in View of the formation of the cylinder bores.

Structural arrangement Referring .now to the. drawings. in vdetail and Fig. 1 thereof in particular, the structure shown therein comprises a primary cylinder body or primary rotor I and a secondary cylinder body or` secondary rotor 2. The rotors I and 2 are mounted in the interior of the hollow shaft@ which represents the output shaft. As .will be clear fromr yactuating the swash'plates I..andfIi.' These.

swash plates are supported by ballbearings I2 and I 3 so as to be rotatable about vthe .longitudinal axis of the drive shaft 29. The ball bearings I2.

and I3 are maintained `in their` positions by the snap rings I4, I5 and I6, I1. The ball bearings I2, I3 have .their outer races mounted in swivel bearings I8 and I9, the studs 20 and 2I of whichV are; rotatably' mounteddn the" ball'bearings 22 and 23. so asto allow .turning of the swivel bear.-

ings I8 and I9 about the axes A-A and B B` respectively. will 'beclearr from .the drawing, the .ball ,bearings .2 2. and. 23.,.are .mounted in ,or

supported by the hol-low outputshaft. Depend- The annularV suring` on .the. positioning .of .the swivel. bearings I8 and I9 in thewell known manner, the two cylin* derbodies--or rotors I and.2 acttogether upon the outputshaft 3 .and,...as .willbe explained later, rotate shaft-.3 .at corresponding..speedsin. its

bearings. and. 26,-.which bearings are mounted inthe transmission casing. 24.

The .primary andsecondary; cylinder bodies .I and 2 are driven by. themotor shaft 21 with flywheel 28 ,throughthe intervention offa splinedintermediate, member. 3|.. which is..connected .to

therflywheel 28 by.screws.3..f While the primary cylinderbody. 4I is. rotateddirectly. by the. drive shaft 29 extending through bore 620i. the control valve 4, the secondary cylinder body 2 .is

rotated at. the required speed, in this instance ata low speed, .by.,shaft.29..through the intervention .of a planetary Igearfsystem, comprising Wheels 33,34and 36.-and the hollow'shaftl. The

sun wheel; 33 .is rigidly `connected to.. the drive4 shaft.29,.while the.planetgears 34 are either directly or by means of bushings 38 journalledonthe planet pins39... Theserpinsare inserted in corresponding ,bor-es. providedin the .planet carrier` 4I)y and are-connectedto thelatter.

hollow shaft 3l. The-internalgear 36. .is connected by screws. 43. to .theclosuremember 4 I. foi` the transmissioncasing 24..

One endofthe hollowshaft 3l. is rotatably journalled :in the bearing 44 of the .outputshaft 3, .while the .other end; ofV shaft- -3'I.-.is provided..

with a splined `portion'llli engaging a correspond-V ingly ,splined portionY of the. secondary cylinder. body 2 similar .to the; engagement-.between the splined portion 630i. drive shaft29,andthecorre.- spondinglysplined portion of theprimary rotor I.

Between the two shafts 29 and .31: there is pro.- vided a pressurey spring 4l.vv Thisspring presses, the two rotors I and 2 againstthe control. sur.-.V

The. planet carrier 40..is preferablyintegral with the.

faces of` controlvalve or ,disci to .thereby cause a corresponding sealing effect for theperiod for which the self-sealing to be brought about by theV formation of the cylinder bores has not yet become effective. As will be seen from Fig. l, the pressure spring 61 acts on one hand upon ring 43 mounted vin the secondary rotor 2, and on the other hand upon .the collar 58 of shaft 29 and upon the snap ring 5 I.

As will be clear from Fig. 4 in connection with Fig. l, the particular embodiment shown by way of example'in these gures is provided with seven hollow pistons 9 reciprocally mounted in the respective cylinders` 6I .of 4.the secondary rotor-2 and adapted` to act upon the swash. plate -.II..- Provided insaid secondary rotor and respectively; communicating withsaidv seven cylinders 6I. are

seven passages GI' as shownin Fig. 5.

As will be seen from. Fig. -6,.the control disci is provided,` in a manner known vper se, .withkidney shaped'control grooves. 6l for controllingthe.;

These grooves. communicate through. passages 66. .with .corresponding control, Igrooves'.

rotor I 37' for, controllingthe rotor 2.

From the above it will be evident that the .Workf i ingV fluid may pass. from the cylinders `I8..in a manner known .per` se, through the .passages Sil@ inrotorA I, throughthe control grooves 6l, the' passages 36, the control. grooves 6l. and the pas.H sages- El. into-thecylinders 6I. of rotor 2,.and. Vice versa, depending, on ,the .angular position of... the swivelA bodies I8 `andIiJ, lwhich means .,on. the position of the swash-plat es l0. and ,II and consequently on. the .i respective piston strokes... The ratio between the R...P. M. of. .the .outputV shaft and the R. P. M. of theinput -shaftde-l pendson `the `ratio between ,the piston .-strokes,

i. e. on .the ratiobetweenthe ,angular positionr of the swivel bodies Il! and I I, based in a manner,`

knownper se von the requirement thattheyolurne of working fluiddelivered bythe rotor I must equal the. volumeof. working iluidreceived. The liquid volume .delivered .by

by. the, rotor 2. the rotor .I, however, equalsthe difference` bef.

tween .the R..P. M. ,of .rotor I andthe R.` P.,M.,. of the output shaft 3 multiplied by thestroke of.

the pistonsil...V Theratio between the R.V P. M.

of theoutput shaft andthe R. of the inputvshaft can .thus clearly be calculated from the. ratio of the angularpositions of the swivel bodies.

Referringnow to Fig. 2 illustrating anaxiaL piston fluidtransmission in which the cylinder bodies or rotors I and 2 are also driven at diiferent speeds, it will be seen that the-arrangementv of Fig.. 2 differs from that of Fig. l in `that the outputv shaft .3a.is integral withthe rotatable.y control valve lla.` The rotors I and V2 areA jour nalledinthe output shaft 3a by means vof .the bushings 6a and la. The pistons 8 and 9 respecfA tively actuate the swash plates Iii and` I I similarV to thecorresponding arrangement ofF-igl. By

meansof the` bearings I2 and I3 and the snap,

rings I4, I5 and IG, Il, the swash plates ,It and II are rotatably securedin the swivel bodies I8 andi!! respectively. The swivel bodiesin their turn are providedwith studs or pivots 28 and 2I respectively movably or,V .rotatably journalled inl the bearings. 22 `and 23 so. as to be able to turn around the axis A-A and B-B ,respecti'velyV The bearings 22 and 23 are mounted in the hol-Y lowoutput shaft 3a. Depending on VVthepositioning ofthe` swivelbodies I8 I9 in the .well knownL manner, thetwo rotorsY I and 2 actuate the out;` put shaft 3a and rotateA thesame at correspond,-r

the angular velocity of `the rotor 2 being different from that of rotor I. The gear 33a. is rigidly connected to the drive shaft 29a. The gears 34a and 35a are either integral with or rigidly connected to their axle 39a which latter is journalled in corresponding bearings 38a, 38h, respectively supported by the closuremembers dla and 42a of the transmission casing 24a. One end of the hollow shaft 31a is rotatably journalled in a bearing 44a of the output shaft 3a, while the other end of the hollow shaft 31a, similar to the drive shaft 29a, is provided with a splined portion 46a engaging a correspondingly splined portion of the rotor 2.

The pressure spring 41a acts on one hand through bearing 49a and snap ring 48a upon the rotor 2, and on the other hand through the collar 50a of drive shaft 29a and snap ring 5Ia upon the rotor I so as to press both, rotor I and rotor 2, against the control surfaces of the rotatable control valve 4a.

The drive shaft 29a and output shaft 3a. have their ends provided with splined portions for engaging connecting members (not shown in the drawings). Similarly, the closure member 42a is provided with a flange 64 for connecting the transmission to and centering the sameon a drive motor.

Referring now to Fig. 3, the structure shown therein corresponds in principle to that of Figs. l and 2. Thus, for instance, the rotor I is likewise directly driven by the drive shaft 29h. In contrast to the arrangements of Figs. 1 and 2, however, the cylinder body 2 does not rotate but is arrested or held stationary by the hollow shaft 3'Ib. To this end, for instancathe hollow `shaft 3'Ib extends through the bearing 26h of the output shaft 3b land is provided at one end with a splined portion 65 engaging a correspondingly splined portion in `the stationary closure member 42h, while a splined portion 46h at the other end of the hollow shaft 3'Ib engages a correspondingly splined portion ofthe cylinder body 2. Inasmuch as the remaining parts of the structure of Fig. 3 have been described already in connection with Figs. 1 and 2, a further description of Fig. 3 appears to be superfluous.

While, for purposes of simplicity, the hollow output shaft 3, 3a, 3b has been shown as an integral piece, it is to be understood that preferably theE hollow output shaft consists of three parts screwed or otherwise connected together along the planes A-A and B-B extending perpendicular to the longitudinal axis of the uid transmission. This subdivision, however, is by no means necessary, if for instance, the bearings 22 and `23 are inserted into corresponding bores of the swivel bodies I8, I9, and the pivots 20, 2| are inserted from the outside into` the output shaft with the stationary closure 42e, while a second splined section 46c of shaft 31o is -in engagement with the body 2. However, in contrast to Fig. 3, in which the swivel body I9 is provided with two pivots 2l, the swivel body |90 of Fig. '7 `is so designed that the pivot bearings 23 areinserted into corresponding bores of the swivel body |90, while the pivots Il are inserted from the outside through bores in the output shaft 3c and are connected `to shaft 3c by means of flange 'IIa and screws 68 as shown in Fig. '7. Furthermore,

in contrast to the arrangements `of Figs. 1 to 6, the left hand swash plate! Illc in Fig.l r7 is not angularly movable but is held in a predetermined inclined position. To this end, the swash plate IIJc is supported in its inclined position by the i radial-axial bearing I2 mounted in the output shaft 3c which, for this purpose, is provided with a corresponding bore and supporting surface,

shown in Fig. '7 turned about an angle of 90"` around its longitudinal axis with regard to its actual position,\in order more clearly to illustrate the arrangement. For purposes of assembly, the output shaft of the structure of Fig; '7 is likewise composedof three parts, namely 3c, 3d, and 3f which are arranged concentrically with regard to each other and are connected to each other by screws 'I0 and 69 respectively. All other parts of Fig. '7 correspond to those described in connection with the preceding figures and are, therefore, numbered accordingly, however, with the suflix c. i

It will be obvious that the plain bearings shown in the drawings may be replaced by ball bearings, roller bearings or conical antifriction bearings and that, on the other hand,\the ball bearings fo'r the swivel bodies as shown in the drawings may be replaced by roller bearings, conical antifriction bearings or plain bearings.

It is, of course, understood that the present invention is, by no means, limited to the particular constructions shown in the drawings but also comprises any modifications within the scope of the appended claims.

What I claim is: `1. An axial piston fluid transmission which comprises in combination, a hollow output shaft, a primary fluid operable cylinder piston arrangement arranged within said output shaft, a secondary fluid operable cylinder piston arrangement mounted within said output shaft, first swash plate means operable by said primary cylinder piston arrangement, second swash plate der piston arrangementsfor `rotating said cylinder bodies.

2. An axial piston fluid transmission which comprises in combination, a hollow output shaft, a primary fluid operable cylinder piston arrangement within said output shaft and including a primary cylinder body, a secondary fluid operable cylinder piston arrangement mounted within said output shaft and including a secondary cylinder body, first swash plate means operable by said primary cylinder piston arrangement, second swash plate means` operable by said secondary fluid operable cylinder piston arrangement, fluid control-means; arranged ffor cooperation rwith` said primary `and said secondary pcylinder- :piston z aia-- rangements, meansy drivingly` connecting said iiirst v and secondzswash.- plate` means with, said output shaft, a drive'shaft; drivingly connected with said primary gcylinderk body,;-and a -planetary gear system drivingly.` interconnecting 'said drive shaft and said secondary cylinder-body for rotating the same.

3)"An axialgpiston fluid transmissioni'which comprisesyin combination, a hollow output shaft,

` a primaryfiiuid-operable cylinder piston arrangement '.arrangedwithinzsaid :output shaft, said primarycylinderfpiston arrangement including a primary cylinder: body, a secondary uid operablecylinder piston-arrangement mounted within said outputshaft and ,including a secondary `cylinder body,f iirst'swash platefmeans operable by said primaryV ,a cylinder pistonarrangement, second swash-platefmeansrl-operable by said secondary fluid 4operable cylinder piston-arrangement, fluid i control means-arranged for` cooperation withsaid primaryand-secondary; cylindcr bodies, a drive shaft directly drivinglyconnected with saidv primary cylinder bodyrfor rotating the sameandr spur` gear,y transmission-means drivingly connecting said fdrive lshaftv withsaid secondary cylinder 1 body.

4. An aX-ial c pi-sten" v-uid 1- transmission which comprises inzcorn-bination, a hollow output shaft;

a primary-fluidoperable cylinder piston arrangement arranged within said output shaft and includingA a `primaryfcylinder body, a secondary uid operable cylinder" piston 1 arrangementI mounted f withinA said f: output shaft and Vvincludinga secondary cylinder body, iirst swash plate" means` oper-,ableg voy-said primary-cylinder piston arrangement, secondswash plate means operable by said secondary flu'idf operable cylinder pistonarrangement,uid control means arranged for-cooperation with said primary and secondary cylinder bod-ies, a vdrive shaft; and reducing transmission-means,drivingly connecting said drive ment arranged within said outputk shaft and in-` cluding va primary cylinder body, a secondari7 fluidv operable cylinder Y piston arrangement mounted within said output shaft and including a secondary cylinder body, first swash plate means operable by said primary cylinder piston arrange-y ment,second swash plate -means operable vby said secondary fluid operable-cylinder piston arrangement, fluid control means arranged for cooperation with said ,primaryiand secondary cylinder bodies, a drive shaft, yand step up transmission means drivingly connecting said .drive shaft with one of said cylinder bodiesfor rotating the same atfa .speed'fhighenthanfthe-.fspeed of. said drive shaft.

6. An axial piston fluid transmission which comprises 'in- Icombination-,1a hollow output shaft, a primary fluid operable'cylinder piston arrangement arrangedrwithin said output shaft'andincluding k'a Yprimary cylinder body, a secondary f fluid roperable` cylinder piston arrangement mountedwithin said output shaftV and including a secondary cylinderbodygrstswash plate means operable vby'saidY primary-cylinder piston arrangement,` second jswash plate vmeans operable byfsaidlsecondaryijflu-dfoperable cylinder piston arrangement, rotatable fluid control valve-means@A commonto said primary'and said fsecondarycyl inder "bodies for cooperation .therewith; a single spring means'arrangedzto press both, said pri-'rv mary `and z said secondary cylinder tbodyf "against fl opposite surfaces ofsaid common fluidi'controlf valve means,; means'. 'drivingly' connecting I"saidia' rst and second swashplate means with said output shaft,` and-la "drive fshaftl d rivingly connected-J with the cylinderibody of bothof said-cylinder r pistonarrangements. i

7. An' axial piston fiuidtransmission, which comprises in combination: a hollow output` shaft,.= a primary cylinder body rotatablymounted with# in said hollo'w outputshaftyprimary piston 'meanszz reciprocablymounted in saidprim'ary cylinder; body, a secondary cylinder body rotatablymount-fed within'said hollow `output shaft, secondarypisa ton means reciprocably mounted in said second-J ary `cylinder body, a drive shaft Adrivinglyconel nected to one of said cylinder bodies to' causesaidiI- one cylinder body to rotate at the,same-speed1asv.f' said drive shaft,i transmission f means, drivingly connected tosaid drive shaft sand to the :otheri cylinder bodyfor yconveying driving power. from'ti said drive shaft also/'to said other cylinder body but so as to drive the latter 'at aispeed different i fromV the `speed of saiddrive shaft-,Jfirst'swash` plate means arranged for cooperation withsa-i'd primary piston meansy second swash'plateV means arranged ifor cooperation withI said secondary-'1 piston means, and means respectively drivinglyf connecting saidfirst 'and .second swashplatef means to said hollowoutput shaft'and adapted. to Si convey 'driving power fromboth Tof' said 'cylinder f bodies and piston means through the swash platesif. pertaining thereto to. said output shaft.`

8.I An axial pistonfiuid i transmission which-J comprises incombination: a hollowoutput'shaft,` a .primary cylinder body.` rotatably mounted witli-t in said hollow output shaft', primary piston-meansv reciprocably mounted in'saidprimary cylinder body, a secondary cylinder body rotatablymount-` ed within said hollowioutputshaft, `secondary piston means reciprocably mounted in said second-f ary lcylinder body, firstswash` plate lmeans ar-y ranged for cooperation with said primary piston means, second swash'plalte means arranged for' cooperation with said secondary piston means, a rst driving shaft extending through/an opening in said hollow output shaft and being' directly,- drivingly connected to one of said cylinder bod-n ies to cause said one vcylinder `body to rotate att the same speed as said first driving shaft', and

a second driving shaft coaxially arranged `with said first driving -shaft and drivingly` connected to both said first driving shaft and the other'one" of said cylinder bodies;

References Cited `in the file of this patent 1 UNITED STATES'. PATENTS Number Name Date 1,197,789 Bluemel Sept.`12,V 1916 1,648,000 Leey Nov; 8, 1927' 2,141,166 Bischof Dec.- 27, 19389- 2,354,597 Janda'sek` July 25j-i944 P 2,432,115 Mayner Dec; 9, i9474 i FOREIGN `*PATENTS Number Country Date 1 23,390 Australia July 6,'1935': 

